Laparoscopy is a minimally invasive surgical procedure that utilizes a small tubular laparoscope, or camera, to view a patient's internal organs. During laparoscopy, trocars are used to puncture the body wall, such as the abdominal wall, to provide access for the camera and thin laparoscopic surgical instruments. Since the incisions in these types of procedures are smaller than with conventional surgery, there is less patient trauma and reduced hospitalization. As a result, laparoscopy continues to grow in popularity.
A trocar assembly generally includes two major components, an obturator and a cannula. The obturator typically includes an elongate body having a sharpened distal tip. The sharp distal tip pierces and cuts the tissue forming the body wall. The cannula generally has a cylindrical configuration and a seal-valve housing. As the trocar is pushed or otherwise moved through the body wall, the sharp distal tip of the obturator functions to cut the tissue and provide an opening for the trocar. Once the trocar is operatively positioned, the obturator can be removed leaving the cannula to provide working access into the body cavity. For example, a laparoscope may be inserted through the cannula to view the body cavity or surgical instruments may be inserted through the cannula to perform ligations or other procedures.
Many surgical procedures are now being performed with the use of trocars. Originally these devices were used for cutting an opening into the body wall to insert and leave a drain tube. Previously these procedures required incisions of many inches. By minimizing the incision length, the stress and loss of blood suffered by patients is minimized and the recovery times of patients can be significantly reduced.
Initial entry into the abdominal cavity is inherently dangerous. The primary trocar insertion is commonly known as “blind entry” because the surgeon is unable to see the internal organs of the patient. Surgeons must take extreme caution to avoid potentially fatal injuries to internal organs and major vessels. Secondary trocar insertions are less dangerous because surgeons have the ability to inspect the body cavity and guide the positioning of the remaining trocars using the laparoscope inserted through the primary opening. However, significant injuries, and even fatalities, caused by secondary obturator cutting tips still occur.
It has been found that a relatively large force is required to push the sharpened tip of an obturator through the body wall. Once the sharpened tip penetrates the body wall, an opening is created by the lateral portions of the blade that permits the trocar to pass into the body cavity. Once the opening is sufficiently large to permit the full diameter of the obturator to pass through, resistance to penetration is removed and the obturator is free to move unrestricted into the body cavity. This sudden drop in resistance when the obturator passes into the cavity is sometimes called the “plunge effect.” In most cases, delicate internal organs are very close to the inside of the body wall being pierced. Most laparoscopic penetrations are only performed after the internal cavity is filled with carbon dioxide, thereby expanding the body wall away from the internal organs, to minimize the danger of accidental injury due to the obturator coming into contact with internal organs. In most cases, however, the force required for penetration and the elastic nature of the body wall cause a severe depression where the trocar is entering the body cavity, thereby bringing the penetrating tip of the instrument closer to the internal organs. Failure to stop this cutting action after the inevitable sudden resistance drop can result in considerable damage to interior organs and other tissues within the cavity.
In an effort to avert these dangers to the patient, trocars have been developed with a variety of safety features and devices. One of the major areas of interest has been in attempting to provide an automatic safety shield to surround and protect the trocar tip immediately upon entry into the body cavity. In a typical configuration, the safety shield is shaped to cover the piercing tip and cutting portions of the blade. In one position, the shield is locked in place so that it covers the piercing tip and the blade. In a second position, the shield is unlocked but is biased in such a manner that, when the shield is not encountering pressure along its lateral axis the shield covers the blade. As the shield encounters pressure along its lateral axis, such as when the trocar is being pushed through a body wall, the shield retracts, thereby exposing the piercing tip and cutting edges of the blade. Once the full width of the blade has cut the body wall to the full diameter of the trocar, the pressure exerted on the shield is eliminated and the shield moves forward to cover the blade and locks in place. The locked shield is intended to protect internal body organs from incidental contact with the piercing tip and injury resulting therefrom. Trocars including various safety shield designs are illustrated in U.S. Pat. No. 4,535,773 issued Aug. 29, 1985 to Yoon, U.S. Pat. No. 4,601,710 issued Jul. 22, 1986 to Moll, U.S. Pat. No. 4,654,030 issued Mar. 31, 1987 to Moll et al, U.S. Pat. No. 6,613,063 issued Sep. 2, 2003 to Hunsberger, U.S. Pat. No. 5,916,232 issued Jun. 29, 1999 to Hart, U.S. Pat. No. 6,497,687 issued Dec. 24, 2002 to Blanco and U.S. Pat. No. 6,063,099 issued May 16, 2000 to Danks, et. al. Although these existing patents disclose improvements over previous trocar devices, they continue to be plagued with a number of problems. In fact, studies have shown that shielded obturators actually offer little or no protection to internal organs or vessels. As the resistance on the trocar drops as the trocar passes through the body wall, the spring-loaded shields do not travel fast enough to cover the cutting tip before the cutting tip comes in contact with internal organs.
Because the shield width on current shielded obturators extends close to the full diameter of the obturator, in some cases abutting the inside diameter of the cannula, the drop in tissue resistance on the shield and its surrounding cannula is virtually simultaneous. Thus, the shield simply cannot travel the distance to cover the cutting portion of the obturator in time to have a protective effect. Furthermore, because current shields have so much surface area, they actually contribute to the resistance force that leads to the dangerous plunge effect. For example, the shielded trocar disclosed in U.S. Pat. No. 5,709,671 utilizes a cutting blade with a diameter that is smaller than the obturator and a single shield configuration that extends to the full diameter of the obturator. In an effort to reduce the wound produced by the trocar, this design unfortunately increases the delay in shield deployment because abdominal wall tissue resists the shield until the full diameter of the cannula penetrates the cavity.
In another common shielded trocar configuration, the safety shield is essentially a tube that surrounds the obturator tip. Even though such a shield is effective in protecting the obturator tip (after the plunge effect), when these units are inserted through the body wall, the tissue surrounding the tubular safety shield offers significant resistance and impedes shield activation. As a result, the entire obturator tip and the shield must be fully inserted into the body cavity before the shield can activate. If extreme care is not exercised, the plunge effect may cause serious internal injury in the instant before the safety shield can achieve a fully extended position. In addition, trocars having these spring-loaded tubular safety shields require larger incisions. Particularly, the incision formed by the obturator generally must extend to the outer diameter of the tubular shield before the resistance of the body wall pressure is decreased to allow the shield to spring forward. It is also not uncommon for these tubular shields to possess a relatively large mass such that considerable time is required to move the shield into the distal or safety position.
U.S. Pat. No. 6,613,063 also describes a shielded obturator with a cutting portion that has a diameter less than the full diameter of the obturator. However, while the '671 shield extends to the full diameter, the '063 shield is significantly smaller than the obturator diameter. Although this design will likely allow the shield to cover the cutting area before the obturator completely enters the abdomen, it will certainly increase the force required to enter the abdomen. In this manner, the obturator described in this invention will function similar to a “blunt” obturator. This can happen for two reasons. First, since the shield has reduced surface area contacting the abdominal wall tissue, it will have a tendency to cover the cutting area if there is not constant resistance on it throughout the trocar insertion. Once the shield covers the cutting area, it locks into place and functions as a blunt obturator. If the surgeon recognizes that the shield has locked, he must stop the insertion, rearm the device, and begin again. Second, even if the obturator functions properly and the shield locks once the cutting area has penetrated the abdominal wall, there will be significant resistance on the obturator during the remainder of the insertion because no cutting surface remains. If the '063 device is constructed with a wider blade, similar to other shielded obturators, it will have the same disadvantages, namely exposed blade entry and delayed shield firing.
U.S. Pat. No. 6,497,687 also describes a mechanism that is designed to allow a shield to cover the entire cutting portion before the full diameter of the obturator enters the body cavity. As with the '063 patent, the shield is designed to spring forward and lock once the cutting tip penetrates the peritoneum. As with current shielded obturators, the cutting surface extends to the full diameter and, therefore, it will likely be necessary for the full diameter of the cutting portion to enter the abdominal cavity before the shield is free to move forward. Also similar to the '063 patent and current shielded obturator designs, only one shield is responsible for covering the entire cutting area. Finally, similar to the '063 patent, the shield will contact less tissue upon insertion, thus any hesitation by the surgeon will cause the shield to prematurely fire and lock.
The majority of shielded obturators are designed with one shield to cover the entire cutting surface. One exception is U.S. Pat. No. 5,275,583. In this design, however, multiple independently moving shields actually function similar to a single shield: each shield is responsible for covering a multiple of intersecting blade surfaces. The design of a single shield to cover an entire cutting surface is less than optimal for at least two reasons. First, if the cutting area extends to the full diameter of the obturator (in an effort to create less force to penetrate the body wall), the single shields will spring forward too late to protect the internal organs from obturator tip. Second, if the cutting area is significantly less than the full diameter of the obturator (in an effort to have the shields cover the cutting tip as quickly as possible), the obturator may require excessive force to enter the body cavity. As mentioned previously, this latter scenario can occur if the shield fires prematurely due to any hesitation upon entry, and the surgeon continues to force the trocar into the patient when the shields are forward and locked. Additionally, if the cutting surface of the obturator tip is too small, even if the shields fire at the appropriate time (upon initial penetration of the peritoneum), excessive force will be required to insert the remaining diameter of the obturator.
In summary, shielded obturator designs have traditionally linked the diameter of the protective shields with the exact diameter of the cutting surface. It is important to note that inexperienced or less-skilled surgeons are the most likely to hesitate, even slightly during trocar insertion. Therefore, it is desirous to have a shielded obturator that not only provides ease of insertion, but also has a mechanism that reduces the chance for premature shield locking.
Another common obturator configuration includes a blade having a symmetrical triangular form. These blades tend to form an opening which results in a wound consisting of three cuts each radiating from a central puncture or penetration point. While it is generally agreed that this blade configuration provides a low entry force, the concern remains that the resulting wound can result in herniation, as well as other complications associated with wound closure and healing.
Other obturators have only a single flat blade. These obturators penetrate the body wall through a single incision which reduces the concerns about wound herniation, closure and healing. In many cases, however, this configuration also fails to provide an incision which accommodates the full diameter of the obturator. As a result, insertion forces required to penetrate the body wall tend to be relatively high. Additionally, forcing a cylindrical shaped trocar through a linear incision can actually result in the propagation of the wound.
Still other trocars on the market utilize blunt obturator tips to reduce the potential for accidental sharp injuries. Such a device is disclosed in U.S. Pat. No. 5,271,380. These devices are not as popular among surgeons because they require excessive force to enter the abdominal cavity. Additional force creates an even more dramatic plunge effect. Because this translates to greater loss of control, it is not surprising that blunt trocars have also been responsible for injuries, sometimes resulting in death. These devices were designed to separate tissue layers rather than cutting through them. Several similar designs have been introduced over the years, however each one exacerbates the plunge effect.
Another common feature to most shielded obturator designs is the locking mechanism. Most shields are designed to lock into place once they cover the entire cutting portion of the obturator. This locking mechanism is used to prevent the shield from being inadvertently retracted, thereby exposing the cutting portion, once the obturator has fully penetrated the body wall. In those cases when the shields prematurely fire and lock before entering the body cavity, various methods are used to unlock the shield and reset the locking mechanism. One problem with the '063 and '687 designs is that any significant decrease in shield diameter will likely cause the shield to prematurely move proximally to cover the cutting portion. This is especially troublesome during the primary insertion because premature locking could falsely indicate to the surgeon that the abdominal cavity has been penetrated. The surgeon may then remove the obturator only to realize that the insertion must be repeated. If the surgeon even slightly hesitates during insertion, the shields in the '063 and '687 patents would likely fire and lock. Optimally, the surgeon would stop penetration and press a lock release button to continue cutting. Multiple rearming of the shielded obturator to enter the body cavity can cause needless frustration. If the shield prematurely fires and the surgeon is unable to rearm the obturator, significant force to enter the abdomen would be required. Finally, problems can arise if the surgeon has entered the cavity, but does not realize it. For example, a surgeon that believes that the trocar is still in the body wall when it is actually resting on bowel could rearm the trocar and enter the bowel.
U.S. Pat. No. 6,063,099 describes a shielded obturator with two locking positions. The single shield is designed to first lock into position over the cutting tip before the entire obturator penetrates the abdomen. Since the lateral cutting edges remain exposed, the obturator should be allowed to finish cutting through the abdominal wall even if the shield is locked into the first position. Unfortunately, this obturator's shield design is similar to other shielded obturators in that only a single shield is responsible for covering the entire cutting area. Like the '687 patent, the shield described in the '099 patent has less distance to travel to cover the cutting tip, and thus will likely prematurely cover the cutting tip before entry into the body cavity. If it does not prematurely fire, it will still be delayed in covering the cutting tip like other shielded obturators. Thus the first locking position does not add any protection to the original single locking design. It is desirous to have a shielded obturator with a shield that locks before the plunge effect occurs. However, as has been previously discussed, it can be disadvantageous to have a shield that prematurely locks. It is commonly known that most trocars, whether sharp or blunt, will likely puncture bowel that has adhered to the inner body wall in the location of the trocar penetration. However, it is far more common to have bowel that loosely adheres to the body wall. In this case, shielded obturators can injure the bowel if the cutting tip precedes the shield, as occurs in most insertions. The double locking mechanism in the '099 patent offers no additional protection to bowel injuries, because, as with loosely adherent bowel, it is important only to have the cutting tip covered, not locked. Only a significant force against a spring-loaded shield will cause it to retract.
Another problem with existing trocar devices is that many employ complicated actuation and locking mechanisms requiring far too much expense and often necessitating costly mated trocar and cannula assemblies. With the current emphasis on cost controls in health care, it is desirable to have simple, lower cost instruments without sacrificing quality.
As can be seen from the foregoing discussion, trocars currently used for laparoscopic surgical procedures do little to prevent injuries to internal organs during insertion and manipulation of the trocar. Although a significant amount of effort has been expended in improving trocar designs, the results are still poor. Present procedures frequently injure internal organs, and the resulting wounds can be serious or even fatal. A need exists for safer trocars, especially given that laparoscopic surgical procedures are likely to become more commonplace in the future. Specifically, there is a need for a shielded obturator to have a shield mechanism that effectively covers the obturator's cutting tip before the plunge effect. It is also desirous to have a shield mechanism that prevents premature locking of the shield. There is also a need for a shielded obturator that reduces the chance of inadvertent injury to the bowel caused by an exposed cutting tip upon abdominal entry.